BEIJING (AP) — China announced an investigation Wednesday into whether the European Union has adopted unfair trade practices in its probes of Chinese companies bidding on projects in the 27-nation bloc. The move is the latest in a brewing trade war between the two economic giants.

The investigation will focus on wind power, photovoltaics, security equipment and electric trains, the Chinese Commerce Ministry said.

The EU has used a new regulation to investigate companies bidding for projects within the European Union. These include a probe into whether Chinese subsidies give wind turbine companies an unfair advantage in the competition for projects in Spain, Greece, France, Romania and Bulgaria.

China accused the European Union of protectionism and “reckless distortion” of the definition of subsidies in response to that investigation. The EU has also investigated Chinese companies bidding for a 455-megawatt solar park in Romania and for the procurement of 20 electric trains in Bulgaria.

The Chinese investigation will be completed before Jan. 10, with a possible extension of three months to April. It was requested by China’s Chamber of Commerce for Import and Export of Machinery and Electronic Products.

The EU imposed provisional tariffs on China-made electric vehicles last week over subsidies that it alleges gives an unfair advantage to automakers exporting from China. In response, China has launched an investigation into European pork exports.

Both the EU and the United States are worried that inexpensive Chinese automobiles could overwhelm their domestic producers and lead to factory layoffs. Chinese auto exports have risen about 30% in the first six months of this year.